Recycling process for vehicle tires

ABSTRACT

A process for manufacturing structures from worn out tires and a parking stop made by that process. Sidewalls are cut from the tire leaving a circular strip, which is cut transversely to produce an elongated approximately rectangular strip. Spaced slits are cut into the long edges of the strips to form slats suitable for use in manufacturing structures. Two slats are bonded together in a face-to-face arrangement to form a unitary pair of bonded slats. Additional pairs of slats are then bonded to the first pair of slats. All slats are bonded with similar sides in contact; that is, tread side to tread side or inside to inside. The resulting beam can have adjacent corners removed to provide a parking stop configuration. Preferably, the slats are bonded with an elastomer or mechanical fasteners such as ring nails or staples. A thick elastomer, having a thickness of at least about ⅛ inch may be coated over the beam. Beams may be combined to form guard rails, walls, panels, etc.

FIELD OF THE INVENTION

This invention relates to the recycling of scrap automobile and trucktires into useful products.

BACKGROUND OF THE INVENTION

Disposing of scrap tires has become a very large environmental problem.Millions of worn out automobile and truck tires are presently beingstored in enormous piles or filling canyons. These piles result invisual pollution and sometimes catch fire, with the resulting large,dense, smoke plumes polluting the air for miles down wind. In additionliquid hydrocarbons may be released into the ground water due topyrolitic reactions as the tires are heated, then burned. These tirepile fires are very difficult to extinguish.

Tires are presently being recycled on a very limited scale. Some areground into particles useful in road building. Others are used in thecreation of artificial reefs to improve lake and ocean fishing. Some areused for barriers around go-cart race tracks. Presently, recycling isconsuming fewer tires than are being added to the waste stream.

Attempts have been made to recycle at least parts of tires intostructural beams and the like. For example, Snyder in U.S. Pat. No.5,096,772 describes a beam forming process in which the sidewalls oftires are cut away, the rubber tread portion is sliced away from thesteel belts. A thin layer of rubber is vulcanized to the belts and thebelts are laminated together. However, this process uses only a smallpercentage of the tire, requires a complex layup to assure that the tirecords are arranged in different directions in succeeding layers and isquite costly.

Tripp in U.S. Pat. No. 5,340,630 describes a process for recycling thetread portion of tires in which the sidewalls are cut away, the treadportions are joined end to end to form two elongated continuous plies,then the two plies are bonded together to form a long two-ply member.This member can be used as a building material. However, this process islimited to a two ply thickness, is subject to delamination and is notdirectly useful as a product other than in fabricating other structures.

Similarly, in U.S. Pat. No. 5,412,921, Tripp describes a method ofmaking a structure similar to an I-beam from the elongated plies made inhis earlier patent, with plies forming the faces of the I-beam and twoplies together forming the I-beam flange. This is a complex, difficultto secure together, assembly. FIG. 6 of the Trip '921 drawing clearlyshows the curvature of tire treads that makes difficult the bonding oftwo plies together to form a double-ply member.

Miller discloses, in U.S. Pat. No. 5,472,750, a method of producinglarge, thick, mats from tires which includes the steps of slitting thesidewalls and pressing the tire flat to form a preform having arectangular center area conforming to the tread and a saw-toothed edgecorresponding to the sidewalls, then stacking and bonding thesepreforms. Problems remain in truly flattening the preforms due to lessersidewall thickness relative to tread thickness. In particular, obtainingtight interlocking of the saw-toothed edges is difficult, since thispattern conforms to the sidewall diameter and sidewall diameters varygreatly.

In U.S. Pat. No. 5,834,083. Pignataro, Jr. describes a tire recyclingprocess including removing sidewalls from the tires, cutting the treadtransversely to form strips, fastening the strips with interlockingdovetails and bonding strips together. This process is difficult andrequires high accuracy in cutting dovetails. Due to the curvature of theinner surface of the tread material, bonding is difficult and likely toresult in bubble formation or central separation of the lamination.

In general, the bonding together of tire tread strips to form two ormore ply laminations has been very difficult and likely to result indelamination in use as a structural member. The edges of the treadstrips, which curve toward the sidewalls, have a lesser circumference.Or, said another way tread strip edges have a shorter length than thestrip centerline when laid flat. This difference makes flattening thetread very difficult.

Therefore, there is a continuing need for improvements in guard railsystems that recycle portions of used tires, that are strong andresilient, are highly resistant to impact damage, that will notdeteriorate when exposed to severe weather and freeze/thaw cycles andthat can be provided with a reinforcing surface coating having anydesired color.

SUMMARY OF THE INVENTION

The above-noted problems, and others, are overcome by a process forrecycling scrap automobile, truck, etc., tires which basically comprisesthe steps of removing the tire sidewalls (which can be ground for roadbuilding particles or other uses), cutting the tread portiontransversely to form an elongated strip, slitting the strip edgestransversely inward toward the tread longitudinal centerline to a depthof about one inch to about the tread longitudinal centerline about every1 to 4 inches to form a slat useful in manufacturing various structures.The slits. are preferably evenly staggered, with a slit on one sidespaced equally between slits on the opposite side.

These slats may then be secured together in unitary pairs, thenadditional slats(individual or added unitary pairs) may be secured toboth sides of the first unitary pair to provide any suitable number oftread laminations to produce the desired product thickness. Whileadhesive bonding of slats is optimum in most cases, producing anoutstanding combination of strength, resiliency and resistance toseparation, mechanical fasteners, such as staples or ring nails, may beused if desired. In some cases both adhesive bonding and mechanicalfasteners may be used.

For many uses, it is desirable that the slats be trimmed to a selectedwidth for an intended purpose. For example, automobile tires can be cutto a 6 inch width, with truck tires capable of producing slats having 7to 10 inch widths. Automobile tires produce slats having lengths ofapproximately 5 to 8 feet, while truck tire slats have lengths ofapproximately 6 to 9 feet. These slats can be cut to any desired lesserlength.

While a beam produced by laminating a plurality of slats may be used asis, in some cases further trimming to a desired configuration or to adesired thickness, width or length may be done. The beams may belaminated together in a staggered relationship to provide thick panelsfor use as walls or other structures. This laminate is useful in a widevariety of products and structures. Two particularly preferred productuses are parking stops of the sort presently generally made fromconcrete and posts and beams used in guard rails, due to the outstandingcombination of overall strength, resiliency and impact energy absorptioncharacteristics of the laminations.

The slats are laminated under high pressure, preferably from about 100to 200 psi. Typically, a steel beam may be hydraulically pressed againstthe slats or beam in an open topped, box-like mold. While slats may haveuneven thickness in some areas due to uneven side to side wear or otherreasons, we have found that laminating at an elevated pressure willproduce structures having substantially uniform thickness. The beam mayhave a plurality of holes through which mechanical fasteners, such asring nails, can be inserted into the material being pressed.

The exterior of a laminated structure may coated with any suitablematerial to seal the surface and provide a desired color. In aparticularly preferred embodiment, a coating of a high strengthelastomer. This will provide an attractive surface of any desired colorand will further reinforce the structure. With such a coating, staplesor other mechanical fasteners are generally sufficient to secure theslats together.

BRIEF DESCRIPTION OF THE DRAWING

Details of the invention, and of preferred embodiments thereof, will befurther understood upon reference to the drawing, wherein:

FIG. 1 is an exploded perspective view of a tire with the sidewalls cutaway and the tread portion transversely cut;

FIG. 2 is a cross section through the tire showing the preferred linesalong which the tire sidewalls are cut;

FIG. 3 is a plan view of a tread portion slat with spaced edge slits;

FIG. 4 is a transverse section through an assembly formed from fourtread slats;

FIG. 5 is an exploded perspective view of a parking stop;

FIG. 6 is a section view through the parking stop of FIG. 5 with anadded elastomer coating;

FIG. 7a is a perspective view of a first embodiment of a guard railusing a plurality of slats;

FIG. 7b is a perspective view of a second embodiment of a guard rail;FIG. 7c is a perspective view of a second embodiment of a guard rail;

FIG. 8 is a perspective view of a beam formed from a plurality of slats;

FIG. 9 is a perspective view, partly cut-away, of a panel made of plurallayers of strips;

FIG. 10 is a flow diagram of a first embodiment of the process of thisinvention; and

FIG. 11 is a flow diagram of a second embodiment of the process.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, there is seen a tire 10 having a circularstrip 12 which is basically the tread portion of the tire and twosidewalls 14. Typically, tire 10 is a conventional automobile or trucktire, which is worn to the point where the depth of tread grooves 16 istoo shallow for safe use of the tire on a vehicle. Other pneumatictires, such as those used on golf carts, bicycles and the like could beused, although the numbers of those tires available is quite small.

Sidewalls 14 are trimmed from the strip 12 by any suitable means. Anysuitable trim line may be used. Optimally, the trim line isapproximately at line 22 in FIG. 2, at the line where the thickness ofthe sidewall expands to become tread, but outside of the belt cords 20.

Once sidewalls 14 have been removed, strip 16 is cut transversely atline 21, producing a long rectangular strip, typically about 6.5 feetfor automobile tires with truck tire slats somewhat longer. Thesidewalls may be recycled in any suitable manner.

As can be seen in FIG. 2, strip 12 is rounded or crowned, with the edgeshaving a smaller circumference than the central portion of the tread. Inthe prior art, attempts were made to bond such strips 12 together.However, since the strip 12 edges are shorter than the central area, theslats will not lie flat. If coated with an adhesive and pressed into aflat assembly of two or more strips 12, initially the laminate mayappear to be flat and uniform. However, the high internal tensioninherent in such an assembly will cause the assembly to delaminateand/or bubble at the strip interfaces, result in great weakening andloss of structural integrity.

As seen in FIG. 3, cutting slits into the edges of tread strip 12 willproduce a slat 15 which is flat and therefore a preform suitable for themanufacture of a variety of structures. Preferably, the tread strip 12is trimmed to a desired width before cutting the slits. Trim lines 23 inFIG. 2 show a preferred trim line.

The slits 24 are critical to the effectiveness of the process and thestructural integrity and strength of the products produced. For a slat15 cut from an automobile or truck tire having a width of about sixinches, the slits are preferably spaced about one to four inches apartand have depths of from about one inch to about the centerline of thestrip. Optimally, the slits are spaced about three inches apart and havedepths of about two inches. For slats 15 cut from truck tires with slatwidths of about seven or eight inches, the optimum slit spacing is aboutthree inches and slit depth is inward to about 40% of the slat width.

In constructing a laminated product, initially two slats 15 are bondedtogether, preferably by an adhesive although staples or other fastenersmay be used in some cases, as described below. The slats 15 are bondedface-to-face with similar sides in contact; that is, grooved outersurfaces together or smooth inner surfaces together. Preferably thesurfaces of slats 15 are buffed or abraded to remove any contaminantsand improve adhesive bonding.

To build up a thick, beam-like, structure, additional pairs of slats 15are bonded to the two initial slats to form a beam 26 as seen in FIG. 4.Preferably, same sides are always bonded together to cancel out crowneffects. Thus, as shown in FIG. 4, the inner surfaces of the next slatsare bonded to inner surfaces of the first pair of slats. In a preferredarrangement, pairs of slats are bonded together, inside surface toinside surface, then these two-slat preforms are further stacked andbonded together to produce structures of the desired thickness, e.g.four, six or eight slats thick.

One preferred final product for this process is a parking stop as seenin FIG. 5. The two upper corners 28 are cut away to leave a beveledupper surface 30. Two or more holes 32 are drilled through the beam toreceive stakes or the like to hold the parking stop in place. This is ahighly effective parking stop that is resilient with some give uponimpact. The parking stop will not break when impacted or subjected tofreeze-thaw cycles as happens with concrete stops and will absorb energywhen the impact is higher than normal, avoiding damage to either thevehicle or the parking stop.

An alternate embodiment of a parking stop is illustrated in FIG. 6.Here, beam 26, after the upper corners are removed, a coat 34 of anelastomer is applied to the beam. Preferably all external surfaces arecoated. The coating should have a thickness of at least about ⅛ in.,with coatings having thickness in the range of from about ⅛ to ⅜ in.being preferred. The elastomer coating may have any desired color, e.g.blue for handicapped parking spaces. Any suitable elastomer coating maybe used. Typical coatings are those applied by spraying to pick up truckbeds and the like. Such coatings are available from the BullhideCorporation, Rhino Linings, Quarry Coatings, Techthane Elastomers andothers and generally comprise a polyurethane resin.

While the slats 15 making up beam 26 may be bonded together with anadhesive, as described above, mechanical fasteners such as ring nails orthe like may be used in the manufacture of this embodiment, if desired,since coating 34 assists in maintaining the beam structure. The ringnails should include nails 37 inserted from the bottom of the structure,closely adjacent to where bevel 41 begins and nails 39 inserted from theflat top portion 43 adjacent to bevel 41. Alternatively, nails could beinserted thought the structure top near the bevels at angles parallel tothe bevel angle with additional nails inserted though the center of thetop, perpendicular to the top.

Another preferred product is illustrated in FIG. 7a . Here, a guard railsystem 38 is made up of laminated beams 26. Posts 40 have slats runningvertically and have a suitable length for embedding a suitable distanceinto the ground. A notch 42 is cut into the upper ends of posts 40 toreceive an elongated rail 44 having a cross section of the sort shown inFIGS. 5 and 6. Rails 44 preferably extend out from posts 40 to receivethe initial impact of a vehicle striking rail system 38. Because of theresiliency of rails 44 and posts 40, the system will give somewhat withimpact, absorbing impact energy and reducing damage to the impactingvehicle, as would happen with a rigid guard rail. Once the impactingvehicle is removed, the rails will substantially return to theiroriginal position rather than bending and crushing as is the case withconventional metal rails. Rails 44 may be secured to posts 40 by anysuitable means, such as the through bolts 46 shown, lag screws,adhesives, etc.

A second embodiment of a guard rail system 38 is shown in FIG. 7b .Here, a square or rectangular rail 44 is mounted in a large notch 50 inpost 52. This arrangement has energy absorbing characteristics andability to return to shape after impact as described above. Because ofthe greater contact area between rail 48 and notch 50, an adhesivebonding between post and rail will generally be sufficient. However,bolts, screws or the like may be used as a further reinforcement of theattachment, if desired.

A third embodiment of a guard rail system 38 is shown in FIG. 7c. Here,post 53 is rectangular in cross section over its entire length,including the portion extending below ground level 55. Rail 55 issecured to the side of post 53 by a through bolt 46 or the like.Preferably the head of bolt 46 is recessed, as seen in the cut-awayportion of rail 55.

As shown in FIG. 8, walls or other large panels 54 may be formed fromthe beams 26 produced by laying up slats 15. Each beam will have alength of around 6 to 8 feet, depending on the circumference of thetires used. These beams 26 may be bonded together in a staggeredrelationship with adhesives, screws, or other suitable fasteners asdesired. The lengths of beams 26 may be trimmed to provide shorterpieces for wall ends, corners and the like.

Walls 54 made as described will be strong and resilient, resistant toimpacts that would cause cracking in a concrete block wall. These wallsmay be coated with an elastomer coating of any desired color, asdescribed above. Walls 54 are particularly suitable for use in buildingtornado rooms and the like.

Another preferred structure using the slats of this invention is shownin FIG. 9. Here, a plurality of slats 26 of predetermined thickness arelaid up adjacent to each other to form overlying layers 58 producing aflexible, high strength panel 56. The direction of layers 58 is rotated90° from layer to layer to provide maximum strength in each direction.

The abutting edges of the slats 26 in each layer 58 may be bonded withany suitable adhesive. Each layer may be secured to contiguous layers inany suitable manner, such as with an adhesive or mechanical fasteners.Ring nails are preferred where mechanical fastening is chosen. Wheninserted into the rubber slats, the resiliency of the rubber causes itto tightly press into the spaces between rings along the nail, verystrongly resisting withdrawal of the nail. Panel 56 is both strong andresilient and can be used as a structural member in construction, and isparticularly suitable for school playgrounds, railroad crossing mats,etc.

A first preferred embodiment of the process of manufacturing variouslaminated products from worn out tires is summarized in the flow diagramof FIG. 10.

The first manufacturing step is removing the sidewalls from the carcassas indicated in block 64, typically by cutting with a knife, sawing etc.This leaves a circular tread strip, with edges that inherently have asmaller circumference than the center portion of the tread.

The circular strip is cut transversely, as indicated in block 66 toproduce an approximately rectangular strip. The strip at this point willnot lie flat and, if bonded to another strip under high pressure, willtend to bubble or delaminate in use.

The strip is then cut to the desired width, as indicated in block 68.Typically, the strip is trimmed with a band saw or other suitable saw.

Spaced slits are cut into the long edges of the strip, as indicated inblock 70, with the spacing and depth described above, to produce theflat slat 15 as described above. These slits are critical to durablebonding, since they allow the slat to lie flat because the tensions inthe edges that are shorter than the longitudinal centerline of the slatare relieved.

Two slats are then pressed and secured together, as indicated in block72 with similar faces in contact. That is, either two outer, treadbearing surfaces or two inner, smooth surfaces are secured together. Inmost cases, the slats are preferably bonded by flexible adhesive.Mechanical fasteners may be used in place of the adhesive, or inaddition to that adhesive, if desired. Preferrably, the slats arepressed at a pressure of about 100 to 200 psi.

Additional bonded pairs of slats are then secured to the first two tolayup the desired overall beam thickness desired, as indicated in block74. The added slats preferably are secured with similar faces incontact, that is, tread surface to tread surface or smooth inner surfaceto smooth inner surface. This arrangement is important to obtaining astraight beam, since bonding other surfaces may distort the beam due tothe tire tread inherent crown.

Typically, the slats are bonded in a press, such as one using anopen-topped mold conforming to the slat width and length, with a sturdysteel beam extending the length of the opening and hydraulic pistons topress the beam down against a stack of slats in the mold. Where theslats are to be secured together with an adhesive that is applied to thecontacting surfaces before placement in the mold. Where the slats are tobe secured together with a mechanical fastener, such as ring nails orstaples, openings may be provided in the beam through which thefasteners may be installed with a conventional nail gun.

The beams produced in block 74 may be cut to length as indicated inblock 76. Or, they may be trimmed to a desired configuration asindicated in block 80. Typically, the configuration may by the parkingstop shown in FIGS. 5 and 6.

The final shaped beam may be coated with a thick elastomer coating ofany desired color, as indicated in block 78. The steps in the sequenceof FIG. 11 may be varied, where suitable and other modifications may bemade to slats and beams between the basic series of steps shown.

An alternative embodiment of the process of this invention isillustrated in the block diagram of FIG. 12. The initial steps are thesame as described in conjunction with the description of FIG. 11. Tiresare selected and provided to the manufacturing facility, as indicated inblock 84. The sidewalls are removed as indicated in block 86. Thetubular strip is then cut transversely as indicated by block 88 toproduce an approximately rectangular strip, which is cupped towards theinside due to the smaller tire edge circumference, as detailed above.The strip is then trimmed to width as shown in block 90.

In a critical step, the long edges of the strip are slit transversely tothe optimum degree, as detailed above and indicated in block 92. Whilethe slits on opposite sides may have any suitable relationship, theslits preferably staggered along the sides, with a slit on one sidebetween slits on the opposite side. Preferably the surfaces of slats 15are buffed or abraded to remove any contaminants and improve adhesivebonding.

A predetermined number of strips having approximately equal lengths andwidths are prepared as described above. A first strip is coated on oneside and placed in a mold that resembles an open topped box, with thecoating upwards. Additional strips are coated with adhesive on bothsides and placed one at a time in the mold, as indicated by block 96. Afinal strip is coated and placed adhesive side down on the stack. Thiscoating series is indicated in block 94. A press platen, typically asteel beam having a surface corresponding to the opening in the mold isplaced over the stack of strips and pressed against the stack, typicallyby hydraulic cylinders, as indicated in block 98.

The press platen has a plurality of small, spaced openings exposing thetop of the strip stack. Mechanical fasteners, such as staples or ringnails, may be inserted into the stack through these holes by aconventional nail gun.

This process produces an extremely sturdy final product, with the stripsvery securely fastened together. If desired, depending on the adhesiveselected, only one of each pair of abutting strip surfaces could becoated with adhesive, rather than coating both surfaces. Further, ifdesired, either the adhesive coating or the mechanical fasteners couldbe omitted without severely weakening product structural integrity.

While certain specific relationships, materials and other parametershave been detailed in the above description of preferred embodiments,those can be varied, where suitable, with similar results. Otherapplications, variation and ramifications of the present invention willoccur to those skilled in the art upon reading the present disclosure.Those are intended to be included within the scope of this invention asdefined in the appended claims.

We claim:
 1. The process of manufacturing structures from worn tires,which comprises the steps of: providing a worn pneumatic tire having acircular tread strip unitary with two sidewalls; removing said sidewallsleaving a tubular slat; cutting said slat transversely forming anapproximately rectangular slat having two long edges, said slat havingan outer, tread, face and an inner, smooth, face; trimming said longedges to form of slat of predetermined width; cutting a plurality ofspaced slits into said long edges, said slits spaced apart from about 1to 4 inches apart along said long edges said slits communicating betweensaid outer tread face and said inner smooth face and extending inwardfrom a first long edge of said two long edges and generally toward asecond long edge of said two long edges; and securing two of said slatstogether with similar faces in face-to-face communication.
 2. Theprocess according to claim 1 including the further step of applyingadditional slats to said two slats, with all slat interfaces havingsimilar faces in contact, to build up a beam of predeterminedconfiguration.
 3. The process according to claim 1 wherein said slatsare secured together with an adhesive.
 4. The process according to claim1 wherein said slats are secured together by inserting mechanicalfasteners through contiguous slats.
 5. The process according to claim 2including the further step of trimming adjacent longitudinal corners ofsaid beam to form a parking stop configuration.
 6. The process accordingto claim 2 including the further step of applying an elastomer coatingto said beam to a thickness of at least about ⅛ inch.
 7. The processaccording to claim 6 wherein said elastomer coating comprises apolyurethane.
 8. The process according to claim 2 for producing a guardrail including the further steps of notching an end of a plurality ofsaid beams and mounting a beam in said notches.
 9. The process accordingto claim 1 wherein said slits along said first long edge liesubstantially along a transverse line equally spaced between said sliLsalong said second long edge.
 10. The process according to claim 9wherein said slat is trimmed to a width of about 6 inches, slits are cutabout 3 inches apart to a depth of about 2 inches.
 11. The processaccording to claim 9 wherein said slat is trimmed to a width of about 7to 8 inches, slits are cut about 3 inches apart to a depth of abouL 40%of the slat width.
 12. The process according to claim 1 wherein saidslits extend from about 1 inch to about one-half the slat width intosaid long edges, said slits along a first long edge lying between slitsalong the second long edge.
 13. The process of manufacturing structuresfrom worn tires, which comprises the steps of: providing a wornpneumatic tire having a circular tread strip unitary with two sidewalls;removing said sidewalls leaving a circular slat; trimming said slat to asubstantially uniform width; cutting said slat transversely forming anapproximately rectangular slat having two short edges and first andsecond long edges, said slat having an outer, tread, face arid an inner,smooth, face; cutting a plurality of spaced Slits into said long edges,said slits spaced from about 1 to 4 inches along said long edges, saidslits communicating between said outer tread face and said inner smoothface and extending from about 1 inch to about one-half the width of saidstrip into said long edges in a direction from one of said long edgestoward the other of said long edges with said slits along said firstlong edge lying between slits along said second long edge; securing twoof said slats together in face-to-face contact of similar faces with ameans selected from the group consisting of adhesives, mechanicalfasteners and combinations thereof, to form a first unitary pair ofslats; and adhesively bonding additional unitary pairs of slats to saidfirst unitary pair of slats, with all slats having similar faces incontact, to build up a beam of predetermined configuration.
 14. Theprocess according to claim 13 including the further step of trimmingadjacent longitudinal corners of said beam to form a parking stopconfiguration.
 15. The process according to claim 13 including thefurther step of applying an elastomer coating to said beam to athickness of at least about ⅛ inch.
 16. The process according to claim15 wherein said elastomer coating comprises a polyurethane.
 17. Theprocess according to claim 13 wherein said slits along said first longedge lie substantially along a transverse line equally spaced betweensaid slits along said other second long edge.
 18. The process accordingto claim 13 wherein said slat is trimmed to a width of about 6 inches,slits are cut about 3 inches apart to a depth of about 2 inches.
 19. Theprocess according to claim 13 wherein said slat is trimmed to a width ofabout 7 to 8 inches, slits are cut about 3 inches apart to a depth ofabout 40% of the slat width.